It is known to convert a ring attached carboxylic acid group to a trichloromethyl group when said acid group is on the ring of a nitrogen heteroaromatic compound and in a position adjacent to a ring nitrogen atom.
One reason for making such conversions is to allow for the preparation of compounds which cannot be prepared by the conventional practice of direct chlorination of methyl groups. For example, compounds containing alkoxy, alkyl or alkoxy or alkyl substituted aryl groups, in addition to the methyl group to be converted, cannot normally be prepared by direct chlorination without chlorination of the above groups.
Most known processes involve treatment of the carboxylic acid compound with phosphorus pentachloride usually in the presence of excess thionyl chloride. Such processes are taught by Takahashi et al. "Kinetic study on the conversion of pyridine and Quinolinecarboxylic acids to the corresponding Trichloromethyl Compound," J. Het. Chem. 15 893 (1978); Chemical Abstracts 74, 125566y; Chemical Abstracts 79 31986m and Chemical Abstracts 81 105395h. Related processes for other types of chlorinations are taught in Chemical Abstracts 63 9901d and U.S. Pat. No. 2,907,798.
Since the known procedures are only useful in the conversion of carboxylic acid groups to trichloromethyl groups when the acid group is adjacent to the nitrogen atom in a nitrogen heteroaromatic cyclic, it would be desirable to find less selective procedures and procedures which can be employed with other than nitrogen heteroaromatics.